Envelope header design in passive optical networks

ABSTRACT

A computer-implemented method of handling Ethernet packets in a passive optical network (PON) is disclosed. The method comprises generating, by the one or more processors, an initial envelope header that indicates that the initial envelope header is not a preamble replacement; transmitting, over the PON, by the one or more processors, the initial envelope header; accessing, by the one or more processors, an eight-byte block from a first Ethernet packet of a plurality of Ethernet packets; in response to the eight-byte block being an Ethernet preamble, generating, by the one or more processors, a first envelope header that indicates that the envelope header is a preamble replacement; and transmitting, over the PON, by the one or more processors, the first envelope header.

PRIORITY CLAIM

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 62/490,483, filed Apr. 26, 2017, andentitled “Envelope Header Design in 100 GB/S PON,” which provisionalapplication is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to 100 gigabit-per-second (GB/s)passive optical networks (PONs) and, in particular, to an envelopeheader design in PONs.

BACKGROUND

Ethernet passive optical networks (EPON) are optical networks thathandle Ethernet packets. The IEEE P802.3ca 100G-EPON Task Force wasestablished in 2015. The main objective of this task force is definingthe physical layer specifications and management parameters for 25 Gb/s,50 Gb/s, and 100 Gb/s PONs. Such 50 Gb/s and 100 Gb/s optical networkunits (ONUs) in the 802.3ca system will contain multiple transceivers.Their traffic is transmitted via multiple wavelength channels inparallel, with each channel working at 25 Gb/s. This type of wavelengthchannel bonding is a key feature of the 802.3ca system.

The original media-independent interface (MII) transmitted data at 100Mbit/s. Extensions to MII, including but not limited to reduced MII(RMII), gigabit MII (GMII), and reduced gigabit MII (RGMII), arecollectively referred to as xMII.

SUMMARY

Various examples are now described to introduce a selection of conceptsin a simplified form that are further described below in the detaileddescription. The Summary is not intended to identify key or essentialfeatures of the claimed subject matter, nor is it intended to limit thescope of the claimed subject matter.

According to one aspect of the present disclosure, there is provided acomputer-implemented method of handling Ethernet packets in a passiveoptical network (PON) that comprises: generating, by the one or moreprocessors, an initial envelope header that indicates that the initialenvelope header is not a preamble replacement; transmitting, over thePON, by the one or more processors, the initial envelope header;accessing, by the one or more processors, an eight-byte block from afirst Ethernet packet of a plurality of Ethernet packets; in response tothe eight-byte block being an Ethernet preamble, generating, by the oneor more processors, a first envelope header that indicates that theenvelope header is a preamble replacement; and transmitting, over thePON, by the one or more processors, the first envelope header.

Optionally, in any of the preceding embodiments, the method furthercomprises: generating, by the one or more processors, a modified secondEthernet packet from a second Ethernet packet of the plurality ofEthernet packets by: replacing a preamble of the second Ethernet packetwith a second envelope header that includes an indication that thesecond envelope header is a preamble replacement; and transmitting, overthe PON, the modified second Ethernet packet.

Optionally, in any of the preceding embodiments, the generating of themodified second Ethernet packet comprises: setting, in the secondenvelope header, a flag that indicates that the modified second Ethernetpacket is encrypted; and encrypting the modified second Ethernet packet.

Optionally, in any of the preceding embodiments, the generating of themodified second Ethernet packet comprises: setting, in the secondenvelope header, a flag that corresponds to an encryption method; andthe encrypting of the modified second Ethernet packet comprisesencrypting the modified second Ethernet packet using the encryptionmethod.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header, the first envelope header, and the modifiedsecond Ethernet packet are part of transmitting an envelope; and thetransmitting of the envelope comprises transmitting an Ethernet fragmentafter the modified second Ethernet packet.

Optionally, in any of the preceding embodiments, the initial envelopeheader comprises: a 1-bit encryption flag; a 1-bit key flag; an 8-bitcyclic redundancy check (CRC) field; and a 6-bit envelope positionalignment marker (EPAM) field.

Optionally, in any of the preceding embodiments, the EPAM field of theinitial envelope header has a value; and the method further comprises:generating, by the one or more processors, a second initial envelopeheader that indicates that the second initial envelope header is not apreamble replacement, wherein the second initial envelope headercomprises a 6-bit EPAM field containing a value that is the same as thevalue of the EPAM field of the initial envelope header; transmitting,over the PON, by the one or more processors, the second initial envelopeheader; generating, by the one or more processors, a modified secondEthernet packet from a second Ethernet packet of the plurality ofEthernet packets by: copying the second Ethernet packet to the secondEthernet frame; and replacing a preamble of the second Ethernet packetwith a second envelope header that includes an indication that thesecond envelope header is a preamble replacement; and transmitting overthe PON, by the one or more processors, the second modified Ethernetpacket.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header over the PON uses a first wavelength; and thetransmitting of the second initial envelope header over the PON uses asecond wavelength.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header and the first envelope header are part oftransmitting an envelope; and the transmitting of the envelope comprisestransmitting an Ethernet fragment.

Optionally, in any of the preceding embodiments, the Ethernet fragmentis after the initial envelope header and before the first envelopeheader.

According to one aspect of the present disclosure, there is provided asystem for transmitting Ethernet packets over a passive optical network(PON) that comprises: a memory storage comprising instructions; one ormore processors in communication with the memory storage, wherein theone or more processors execute the instructions to perform: generatingan initial envelope header that indicates that the initial envelopeheader is not a preamble replacement; transmitting, over the PON, theinitial envelope header; accessing an eight-byte block from a firstEthernet packet of a plurality of Ethernet packets; in response to theeight-byte block being an Ethernet preamble, generating a first envelopeheader that indicates that the envelope header is a preamblereplacement; and transmitting, over the PON, the first envelope header.

Optionally, in any of the preceding embodiments, the one or moreprocessors further perform: generating a modified second Ethernet packetfrom a second Ethernet packet of the plurality of Ethernet packets by:replacing a preamble of the second Ethernet packet with a secondenvelope header that includes an indication that the second envelopeheader is a preamble replacement; and transmitting, over the PON, themodified second Ethernet packet.

Optionally, in any of the preceding embodiments, the generating of themodified second Ethernet packet comprises: setting, in the secondenvelope header, a flag that indicates that the modified second Ethernetpacket is encrypted; and encrypting the modified second Ethernet packet.

Optionally, in any of the preceding embodiments, the generating of themodified second Ethernet packet comprises: setting, in the secondenvelope header, a flag that corresponds to an encryption method; andthe encrypting of the modified second Ethernet packet comprisesencrypting the modified second Ethernet packet using the encryptionmethod.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header, the first envelope header, and the modifiedsecond Ethernet packet are part of transmitting an envelope; and thetransmitting of the envelope comprises transmitting an Ethernet fragmentafter the modified second Ethernet packet.

Optionally, in any of the preceding embodiments, the initial envelopeheader comprises: a 1-bit encryption flag; a 1-bit key flag; an 8-bitcyclic redundancy check (CRC) field; and a 6-bit envelope positionalignment marker (EPAM) field.

Optionally, in any of the preceding embodiments, the EPAM field of theinitial envelope header has a value; and the one or more processorsfurther perform: generating a second initial envelope header thatindicates that the second initial envelope header is not a preamblereplacement, wherein the second initial envelope header comprises a6-bit EPAM field containing a value that is the same as the value of theEPAM field of the initial envelope header; transmitting, over the PON,the second initial envelope header; generating a modified secondEthernet packet from a second Ethernet packet of the plurality ofEthernet packets by: copying the second Ethernet packet to the secondEthernet frame; and replacing a preamble of the second Ethernet packetwith a second envelope header that includes an indication that thesecond envelope header is a preamble replacement; and transmitting, overthe PON, the second modified Ethernet packet.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header over the PON uses a first wavelength; and thetransmitting of the second initial envelope header over the PON uses asecond wavelength.

Optionally, in any of the preceding embodiments, the transmitting of theinitial envelope header and the first envelope header are part oftransmitting an envelope; and the envelope comprises an Ethernetfragment.

According to one aspect of the present disclosure, there is provided anon-transitory computer-readable medium storing computer instructions,wherein the instructions, when executed by one or more processors, causethe one or more processors to perform steps of: generating an initialenvelope header that indicates that the initial envelope header is not apreamble replacement; transmitting, over a passive optical network(PON), the initial envelope header; accessing an eight-byte block from afirst Ethernet packet of a plurality of Ethernet packets; in response toeight-byte block being an Ethernet preamble, generating a first envelopeheader that indicates that the envelope header is a preamblereplacement; and transmitting, over the PON, the first envelope header.

Any one of the foregoing examples may be combined with any one or moreof the other foregoing examples to create a new embodiment within thescope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an example envelope header structure,according to some example embodiments.

FIG. 2 is an illustration of an example envelope header structure,according to some example embodiments.

FIG. 3 is an illustration of example envelope header structures,according to some example embodiments.

FIG. 4 is an illustration of example envelope header structures,according to some example embodiments.

FIG. 5 is a block diagram illustrating circuitry for clients and serversthat implement algorithms and perform methods, according to some exampleembodiments.

FIG. 6 is a flowchart illustrating a method of handling Ethernetpackets, according to some example embodiments.

FIG. 7 is an illustration of an example envelope, according to someexample embodiments.

FIG. 8 is a flowchart illustrating a method of handling Ethernetpackets, according to some example embodiments.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which are shown, by way ofillustration, specific embodiments which may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the inventive subject matter, and it is to beunderstood that other embodiments may be utilized and that structural,logical, and electrical changes may be made without departing from thescope of the present disclosure. The following description of exampleembodiments is, therefore, not to be taken in a limiting sense, and thescope of the present disclosure is defined by the appended claims.

The functions or algorithms described herein may be implemented insoftware, in one embodiment. The software may consist ofcomputer-executable instructions stored on computer-readable media or acomputer-readable storage device such as one or more non-transitorymemories or other types of hardware-based storage devices, either localor networked. The software may be executed on a digital signalprocessor, application-specific integrated circuit (ASIC), programmabledata plane chip, field-programmable gate array (FPGA), microprocessor,or other type of processor operating on a computer system, such as aswitch, server, or other computer system, turning such a computer systeminto a specifically programmed machine.

In order to coordinate a bonded traffic transmission, the IEEE PON mediaaccess control (MAC) reconciliation sublayer (RS) is extended into amulti-point reconciliation sublayer (MPRS). A bonded transmission is onein which multiple wavelengths are used to simultaneously transmitrelated data frames from one end station to another (e.g., from an ONUto an optical line terminal (OLT) or vice versa). For example, a streamof Ethernet packets may be transmitted by sending each packet in a dataframe. By transmitting a data frame on more than one channelsimultaneously, the bandwidth of the connection is multiplied.

In existing systems, coordination of data sent on multiple channels isdifficult, because the data frames sent on each channel do not includeany coordination information. As discussed herein, user frames areencapsulated into “envelopes,” with each envelope including a header anddata. The data portion of an envelope may also be referred to as apayload. The envelope header may carry important information todelineate the envelope and envelope data, to control data reassembly, tooptionally encrypt/decrypt the envelope data, or any suitablecombination thereof. Thus, use of the described headers facilitatescoordination of data sent on multiple channels. In the followingdiscussion, envelopes applicable for IEEE 802.3ca 100GE-PON are cited asexamples. In a more general sense, the invention is applicable to anytype of multiple lane (or channel bonding) PON systems. Information inthe envelope headers may be used by a receiving ONU to reassemble themultiple received data streams on the multiple wavelengths into a singledata stream.

FIG. 1 is an illustration of an example envelope header structure 100,according to some example embodiments. The envelope header structure 100comprises 64 bits and consists of a control byte 120, a logic linkidentifier (LLID) 130, an encryption flag 140, a key flag 150, anenvelope position alignment marker (EPAM) 160, an envelope length 180,and a cyclic redundancy check (CRC) 190. In EPON, 32 bits of data(transmit data, also referred to as TXD) along with a 4-bit transmitcontrol nibble (TXC) are transferred at a time using an xMII interface.There is one xMII interface for each wavelength. Each bit of a transmitcontrol nibble indicates whether a corresponding byte of the TXD is acontrol byte. Accordingly, the 64-bit envelope header structure 100 issent as two consecutive 32-bit T×D values, each TXD value having acorresponding TXC. Thus, the transmit control nibble 110 has a value of0x8 (1000 in binary), indicating that the first byte of the envelopeheader structure 100 is a control byte (the control byte 120) and thetransmit control nibble 170 has a value of 0x0 (0000 in binary),indicating that none of the last four bytes of the envelope headerstructure 100 are control bytes. Non-header data (e.g., Ethernet frames)does not include control bytes, so the value of the TXC for non-headerdata should be 0.

The control byte 120, 8 bits, is a control byte to delineate thebeginning of an envelope. One or more bits of the control byte 120 mayindicate that the envelope is a first envelope in a sequence or acontinuation envelope in the sequence. In some example embodiments, thecontrol byte 120 is a Start Control code with a value of 0xFB, alsoreferred to as /S/ in the IEEE 802.3ca specification.

The LLID 130, 16 bits, is a logic link identifier to identify thetraffic bearer and destination of the envelope data.

The encryption flag 140, 1 bit, indicates whether the payload isencrypted. If the encryption flag 140 is set to 1, the payload isencrypted; while data encryption is disabled if the flag is cleared. Thekey flag 150, 1 bit, indicates which data encryption key to use.Depending on the value of the key flag 150, either a first key or asecond key is used. Accordingly, a computer, such as the computer 500 ofFIG. 5, that receives the envelope header structure 100 may decrypt thepayload in response to a determination that the encryption flag 140 isset to 1, using a key selected based on the value of the key flag 150.While one key is in use, the other key may be received in an envelopepayload.

The EPAM 160, 6 bits, is an envelope position alignment marker. Whenmultiple envelopes are sent simultaneously using different wavelengths,the value of the EPAM 160 is set by the transmitter to be the same foreach of the multiple envelopes. The transmitter increments the value ofthe EPAM after each 64-bit transmission. Thus, the receiver can use theEPAM values of the received envelopes to correctly order the envelopes,even if the transmission delays for the different wavelengths aredifferent. The receiver may add received data to a memory store that canstore enough data to account for the maximum variable delay between thechannels. The initial EPAM value serves as a row pointer into the memorystore for data placement. The receiver pulls data from the memory storein row sequential order, thus the envelopes may be processed as thoughthey had been received simultaneously.

The envelope length 180, 24 bits, is the length, in 64-bit blocks, ofthe envelope data including the envelope header. The envelope headeritself is one 64-bit block. Thus, the minimum valid value for theenvelope length 180 is 1, indicating that the envelope consists solelyof the envelope header. An envelope having the maximum value of 0xFFFFFF(Ser. No. 16/777,215) 64-bit blocks would include 134,217,720 bytes ofenvelope data. A 64-bit block of an envelope is also referred to as anenvelope quantum (EQ). In various example embodiments, more or fewerbits are used for the envelope length 180. For example, 22 bits may beused for the envelope length 180.

The CRC 190, 8 bits, is the CRC error-detecting code of the envelopeheader and covers all fields in the envelope header. For example, inFIG. 1, the CRC 190 covers the envelope header fields of the controlbyte 120, the LLID 130, the encryption flag 140, the key flag 150, theEPAM 160, and the envelope length 180. By comparing the value of the CRC190 with an independently-computed CRC value from the covered fields,the receiver can detect errors that may have occurred duringtransmission.

FIG. 2 is an illustration of an example envelope header structure 200,according to some example embodiments. The example envelope headerstructure 200 comprises 64 bits and consists of a first control byte210, an LLID 130, reserved bits 230, an EPAM 160, a second control byte250, an envelope length 260, padding 270, a preamble flag (PF) 280, andthe CRC 190. The LLID 130 and the EPAM 160 are described above withrespect to FIG. 1.

The first control byte 210 and the second control byte 250 are each 8bits and together delineate the beginning of an envelope. In someexample embodiments, the control bytes 210 and 250 indicate that the two32-bit words of the envelope header structure comprise an ordered set.The reserved bits 230 are two bits. In some example embodiments, thefirst bit is an encryption flag that indicates data encryption status.The payload of the envelope is encrypted when the encryption flag is setand is not encrypted when the encryption flag is cleared. In theseexample embodiments, the second bit of the reserved bits 230 is a keyflag that indicates the data encryption key to use when encryption isused. In other example embodiments, the reserved bits 230 may becombined with the EPAM 160 to duplicate the function of a data overcable service interface specification (DOCSIS) provisioning of EPON(DPoE) security byte.

The envelope length 260, 11 bits, is the length in 64-bit blocks of theenvelope data following the envelope header. Thus, an envelope using theenvelope header structure 200 may have 0-16,380 bytes of envelope data.The padding 270 is four bits and has a default value of 0000.

The PF 280, 1 bit, indicates preamble replacement status; this envelopeheader is a preamble replacement when PF=1, this envelope header is nota preamble replacement when PF=0. In alternative embodiments, the PF 280is replaced with a start flag that indicates that the envelope is apreamble replacement when the flag is 0 and that the envelope is not apreamble replacement when the flag is 1. The envelope may start with anenvelope header that is not a preamble replacement and include multipleEthernet frames within the envelope. Each Ethernet frame may include anenvelope header that is a preamble replacement, replacing the preambleof the Ethernet frame. In case of a transmission error in which anenvelope is only partially received, the last successfully-receivedEthernet frame may be identified based on the preamble-replacingenvelope header of that Ethernet frame (e.g., based on the envelopelength value in the header).

The CRC 190, 8 bits, covers all fields of the envelope header structure220: the first control byte 210, the LLID 130, reserved bits 230, theEPAM 160, the second control byte 250, the envelope length 260, thepadding 270, and the PF 280.

FIG. 3 is an illustration of example envelope header structures 330,340, 350, and 360, according to some example embodiments. The envelopeheader structures 330, 340, 350, 360 may be used in the modifiedEthernet packet 320 in place of the preamble of a standard Ethernetpacket 310. Envelope header designs other than the envelope headerstructures 100 and 200 are within the scope of the present disclosure.For example, FIG. 3 shows four additional options for the 64-bitenvelope header structure.

The standard Ethernet packet 310 includes a 64-bit preamble, adestination address, a source address, a length/type field, a protocoldata unit (PDU), and a frame check sequence (FCS). The preamble may be afixed sequence of bytes represented by the sequence of hexadecimalvalues: 0x55 0x55 0x55 0x55 0x55 0x55 0x55 0xD5. The modified Ethernetpacket 320 includes a 64-bit envelope header in place of the preamble ofthe standard Ethernet packet 310, and otherwise is the same as thestandard Ethernet packet 310.

The envelope header structure 330 includes control bytes 210 and 250,the LLID 130, reserved bits 333, an EPAM 334, the envelope length 260,and padding 337. The LLID 130 is described above with respect to FIG. 1.The control bytes 210 and 250 and the envelope length 260 are describedabove with respect to FIG. 2. The reserved bits 333 are three bits thatshould be set to 0. The EPAM 334 is a five-bit envelope positionalignment marker. The padding 337 is 13 bits that should be set to 0.

The envelope header structure 340 includes control bytes 210 and 250,the LLID 130, reserved bits 343, the EPAM 160, the envelope length 260,and hybrid error correction (HEC) 347. The LLID 130 and the EPAM 160 aredescribed above with respect to FIG. 1. The control bytes 210 and 250and the envelope length 260 are described above with respect to FIG. 2.The reserved bits 343 are two bits that should be set to 0, in someexample embodiments. The HEC 347 is a thirteen-bit value that providesgreater error-checking and recovery features than CRC 190. In someexample embodiments the 6-bit EPAM 160 is combined with the two reservedhits 343 to duplicate the function of a DPoE security byte.

The envelope header structure 350 includes the control byte 120, theLLID 130, the reserved bits 343, the EPAM 160, padding 355 and 357, theenvelope length 260, and the CRC 190. The control byte 120, the LLID130, the EPAM 160, and the CRC 190 are described above with respect toFIG. 1. The envelope length 260 is described above with respect to FIG.2. The padding 355 comprises eight hits that should be set to 0, in someexample embodiments. The padding 357 comprises five bits that should beset to 0, in some example embodiments. In some example embodiments, the6-bit EPAM 160 is combined with the two reserved bits 343 to duplicatethe function of a DPoE security byte. In some example embodiments, astandard start control code in control byte 120 indicates preamblereplacement. In other words, when a receiver recognizes the standardcontrol byte 120 in the modified Ethernet packet 320, the receiver canrecreate the standard Ethernet packet 310 by replacing the envelopeheader with an Ethernet preamble. Two different envelope headerstructures may be used by the transmitter and distinguished by therecipient based on the first control byte. For example, the envelopeheader structure 350 may be used when the envelope header replaces apreamble and the envelope header structure 330 may be used for a headerthat does not replace a preamble. Since the first control byte 210 ofthe envelope header structure 330 is in the same position as the controlbyte 120 of the envelope header structure 200, the receiver can checkthat byte to determine which envelope header structure is beingprocessed and interpret the remaining fields of the envelope headeraccordingly.

The envelope header structure 360 includes the control byte 120, theLLID 130, the reserved bits 343, the EPAM 160, padding 365 and 367, theenvelope length 260, the PF 280, and the CRC 190. The control byte 120,the LLID 130, the EPAM 160, and the CRC 190 are described above withrespect to FIG. 1. The envelope length 260 and the PF 280 are describedabove with respect to FIG. 2. The padding 365 comprises eight bits thatshould be set to 0, in some example embodiments. The padding 367comprises four bits that should be set to 0, in some exampleembodiments. In some example embodiments the 6-bit EPAM 160 is combinedwith the two reserved bits 343 to duplicate the function of a DPoEsecurity byte. The control byte 120 may comprise a standard startcontrol code that indicates preamble replacement.

FIG. 4 is an illustration of example envelope header structures 400 and450, according to some example embodiments. The envelope headerstructure 400 includes the control byte 120, the LLID 130, theencryption flag 140, the key flag 150, the EPAM 160, a channelassignment field 415, padding 420 and 425, the envelope length 260, thePF 280, and the CRC 190. The envelope header structure 450 includes thecontrol byte 120, the LLID 130, the reserved bits 230, the EPAM 160,padding 465, the envelope length 260, the channel assignment field 415,the PF 280, and the CRC 190. The control byte 120, the LLID 130, theencryption flag 140, the key flag 150, the EPAM 160, and the CRC 190 aredescribed above with respect to FIG. 1. The envelope length 260 and thePF 280 are described above with respect to FIG. 2. The padding 420 and425 are four bits each. The padding 465 is eight bits.

The control nibbles 405 and 410 indicate that the first byte of theenvelope header structure 400 is a control byte and the remaining bytesof the envelope header structure 400 are not control bytes. The controlnibbles 455 and 460 indicate that the first byte of the envelope headerstructure 450 is a control byte and the remaining bytes of the envelopeheader structure 450 are not control bytes

In some example embodiments, channel information is carried in theenvelope header. The channel information helps the receiver to confirmthat received envelopes come from the correct channels. In a specialcase when one envelope applies to multiple channels, the channelinformation in the envelope header clarifies this multiple channelapplication. The channel information may be a bit-mapped 4-bit field,with each bit representing a different channel in the PON system.

The envelope header structures 400 and 450 are two examples of carryingsuch channel information in the envelope header. The channel assignmentfield 415, 4-bits, is a bitmap representing the wavelength channels thisenvelope applies to. Table 1, below, lists the channel assignment bitmapdetails, in some example embodiments.

TABLE 1 Channel Assignment field definition Bit content 0 (LSB) 0—Thisenvelope doesn't apply to Channel 0 1—This envelope applies to Channel 01 0—This envelope doesn't apply to Channel 1 1—This envelope applies toChannel 1 2 0—This envelope doesn't apply to Channel 2 1—This envelopeapplies to Channel 2 3 (MSB) 0—This envelope doesn't apply to Channel 31—This envelope applies to Channel 3

The envelope header structures of FIGS. 1-4 may be implemented in ageneral-purpose computer modified (e.g., configured or programmed) bysoftware to be a special-purpose computer to utilize the envelope headerstructures. For example, a computer system able to implement any one ormore of the methodologies described herein is discussed below withrespect to FIG. 5.

FIG. 5 is a block diagram illustrating circuitry for implementingalgorithms and performing methods, according to example embodiments. Allcomponents need not be used in various embodiments. For example, an ONUand an OLT may each use a different set of components.

One example computing device in the form of a computer 500 (alsoreferred to as computing device 500 and computer system 500) may includea processor 505, memory storage 510, removable storage 515,non-removable storage 520, input interface 525, output interface 530,and communication interface 535, all connected by a bus 540. Althoughthe example computing device is illustrated and described as thecomputer 500, the computing device may be in different forms indifferent embodiments.

The memory storage 510 may include volatile memory 545 and/ornon-volatile memory 550, and may store a program 555. The computer 500may include—or have access to a computing environment that includes—avariety of computer-readable media, such as the volatile memory 545, thenon-volatile memory 550, the removable storage 515, and/or thenon-removable storage 520. Computer storage includes random-accessmemory (RAM), read-only memory (ROM), erasable programmable read-onlymemory (EPROM), electrically erasable programmable read-only memory(EEPROM), flash memory or other memory technologies, compact discread-only memory (CD ROM), digital versatile disks (DVD) or otheroptical disk storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium capableof storing computer-readable instructions.

Computer-readable instructions stored on a computer-readable medium(e.g., the program 555 stored in the memory 510) are executable by theprocessor 505 of the computer 500. A hard drive, CD-ROM, and RAM aresome examples of articles including a non-transitory computer-readablemedium such as a storage device. The terms “computer-readable medium”and “storage device” do not include carrier waves to the extent thatcarrier waves are deemed too transitory. “Computer-readablenon-transitory media” includes all types of computer-readable media,including magnetic storage media, optical storage media, flash media,and solid-state storage media. It should be understood that software canbe installed in and sold with a computer. Alternatively, the softwarecan be obtained and loaded into the computer, including obtaining thesoftware through a physical medium or distribution system, including,for example, from a server owned by the software creator or from aserver not owned but used by the software creator. The software can bestored on a server for distribution over the Internet, for example.

The program 555 may utilize the envelope header structure using modulessuch as a communication module, a flow scheduling module, and a flowcoordinating module. Any one or more of the modules described herein maybe implemented using hardware (e.g., a processor of a machine, anapplication-specific integrated circuit (ASIC), field-programmable gatearray (FPGA), or any suitable combination thereof). Moreover, any two ormore of these modules may be combined into a single module, and thefunctions described herein for a single module may be subdivided amongmultiple modules. Furthermore, according to various example embodiments,modules described herein as being implemented within a single machine,database, or device may be distributed across multiple machines,databases, or devices.

FIG. 6 is a flowchart illustrating a method 600 of handling Ethernetpackets, according to some example embodiments. The method 600 includesoperations 610, 620, 630, 640, 650, 660, and 670 and may be performed bya computer 500 transmitting data over a network. The computer 500 may bean ONU in an optical network that transmits data over the opticalnetwork.

In operation 610, the computer 500 generates an initial envelope headerthat indicates that the initial envelope header is not a preamblereplacement. For example, the envelope header structure 200 may be used,with PF 280 set to zero. A data structure comprising a list of Ethernetpackets may have been provided prior to execution of the method 600. Thetotal size of the Ethernet packets, measured in EQs, may be determinedand, if smaller than the envelope size limit, included in the envelopelength 260. If the total size of the Ethernet packets is greater thanthe envelope size limit, the envelope is filled to capacity and theremaining Ethernet packets and packet fragment (e.g., the remainingportion of a partial Ethernet packet at the end of this envelope) may besent in a subsequent envelope. In operation 620, the computer 500transmits the initial envelope header over a network.

In operation 630, the computer 500 retrieves an eight byte block from anEthernet packet of a plurality of Ethernet packets. For example, apointer to the next EQ to be transmitted may be initialized to thebeginning of the data structure comprising the list of Ethernet packetsand incremented after each eight-byte block is retrieved. The datastructure may include Ethernet fragments as well as complete Ethernetpackets. For example, if the previous envelope ended with a firstportion of an Ethernet packet, the current envelope may begin with anending portion of the Ethernet packet. Similarly, if the total length ofthe Ethernet packets to be sent exceeds the envelope length, the currentenvelope may end with a beginning portion of an Ethernet packet.

In operation 640, the computer 500 determines if the eight-byte block isan Ethernet preamble. If the eight-byte block is an Ethernet preamble,the computer 500 transmits, over the network, an envelope header thatindicates that the envelope header is a preamble replacement (operation660). For example, the envelope header structure 200 may be used, withPF 280 set to one. If the eight-byte block is not an Ethernet preamble,the computer 500 transmits the retrieved eight-byte block over thenetwork (operation 650).

In operation 670, the computer 500 determines if the transmission of theenvelope is complete. For example, a number of EQs transmitted duringthe method 600 may be compared to the number of EQs of the datastructure received prior to execution of the method 600. If thetransmission is complete, the method 600 ends. Otherwise, the method 600continues by returning to operation 630 and processing additional data.

Thus, as operation 630 iterates over all eight-byte blocks of anEthernet packet, the entire Ethernet packet is transmitted over thenetwork with the exception of the preamble, which is replaced by anenvelope header. The result is a modified Ethernet packet having thestructure of the modified Ethernet packet 320, described above withrespect to FIG. 3.

FIG. 7 is an illustration of example envelopes 700 and 750, according tosome example embodiments. The example envelope 700 includes an initialenvelope header structure 705, envelope header structures 710, 720, and730, and Ethernet frames 715, 725, and 735. The Ethernet frames 715,725, and 735 do not include preambles. Thus, by comparison with theEthernet packet 310, the Ethernet frames 715, 725, and 735 include thedestination address, the source address, the length/type field, the PDU,and the FCS, but not the preamble. In the envelope 700, the preambles ofthe Ethernet frames 715, 725, and 735 have been replaced by the envelopeheader structures 710, 720, and 730. The replacement envelope headerstructures include a PF flag that is set to one (or a start flag set tozero) to indicate that the envelope header structures are in place of apreamble. The initial envelope header structure 705 includes a PF flagthat is set to zero (or a start flag set to one) to indicate that theinitial envelope header structure 705 is a header for the entireenvelope 700, not just a single Ethernet frame 715, 725, or 735.

The example envelope 750 includes an initial envelope header structure755, envelope header structures 765, 775, and 785, Ethernet frames 770and 780, and Ethernet frame fragments 760 and 790. In the envelope 750,the preambles of the Ethernet frames 770 and 780 as well as the preambleof the Ethernet frame fragment 790 have been replaced by the envelopeheader structures 765, 775, and 785. The replacement envelope headerstructures include a PF flag that is set to one (or a start flag set tozero) to indicate that the envelope header structures are in place of apreamble. The initial envelope header structure 755 includes a PF flagthat is set to zero (or a start flag set to one) to indicate that theinitial envelope header structure 755 is a header for the entireenvelope 750, not just a single Ethernet frame or frame fragment.

The Ethernet frame fragment 790 is a first portion of a third Ethernetframe. The example envelope 750 may contain a number of EQs insufficientto contain the entirety of the third Ethernet frame. Accordingly, thefirst portion of the third Ethernet frame is included in the exampleenvelope 750 and the remainder (or at least a second portion) isincluded in the next envelope. The Ethernet frame fragment 760 is a lastportion of the first Ethernet frame. The prior envelope may haveincluded the first portion of the first Ethernet frame. Thus, thereceiver can recover the first Ethernet frame by concatenating theEthernet frame fragment 760 to the final Ethernet frame fragment of thepreceding envelope.

FIG. 8 is a flowchart illustrating a method 800 of handling Ethernetpackets, according to some example embodiments. The method 800 includesoperations 810, 820, 830, 840, and 850 and may be performed by acomputer 500 transmitting data over a PON. The computer 500 may be anONU in an optical network that transmits data over the optical network.

In operation 810, the computer 500 generates an initial envelope headerthat indicates that the initial envelope header is not a preamblereplacement. For example, the envelope header structure 200 may be used,with PF 280 set to zero. A data structure comprising a list of Ethernetpackets may have been provided prior to execution of the method 800. Thetotal size of the Ethernet packets, measured in EQs, may be determinedand, if smaller than the envelope size limit, included in the envelopelength 260. If the total size of the Ethernet packets is greater thanthe envelope size limit, the envelope is filled to capacity and theremaining Ethernet packets and packet fragment (e.g., the remainingportion of a partial Ethernet packet at the end of this envelope) may besent in a subsequent envelope. In operation 820, the computer 500transmits the initial envelope header over a PON.

In operation 830, the computer 500 accesses an eight-byte block from afirst Ethernet packet of a plurality of Ethernet packets. In operation840, the computer 500 generates, in response to the eight-byte blockbeing an Ethernet preamble, a first envelope header that indicates thatthe first envelope header is a preamble replacement. For example, theenvelope header structure 200 may be used, with PF 280 set to one. Inoperation 850, the computer 500 transmits the first envelope header overthe PON. Thus, in conjunction with the transmission of the remainingbytes of the first Ethernet packet, the receiver will receive the sameamount of data as for a standard Ethernet packet, but will be betterable to process that data by virtue of the additional informationincluded in the first envelope header as compared to an Ethernetpreamble.

Although a few embodiments have been described in detail above, othermodifications are possible. Other components may be added to, or removedfrom, the described systems. Other embodiments may be within the scopeof the following claims.

What is claimed is:
 1. A computer-implemented method of handlingEthernet packets in a passive optical network (PON) comprising:generating, by the one or more processors, an initial envelope headerthat indicates that the initial envelope header is not a preamblereplacement; transmitting, over the PON, by the one or more processors,the initial envelope header; accessing, by the one or more processors,an eight-byte block from a first Ethernet packet of a plurality ofEthernet packets; in response to the eight-byte block being an Ethernetpreamble, generating, by the one or more processors, a first envelopeheader that indicates that the first envelope header is a preamblereplacement; transmitting, over the PON, by the one or more processors,the first envelope header; generating a modified second Ethernet packetfrom a second Ethernet packet of the plurality of Ethernet packets byreplacing a preamble of the second Ethernet packet with a secondenvelope header that includes an indication that the second envelopeheader is a preamble replacement; and transmitting, over the PON, themodified second Ethernet packet; wherein the transmitting of the initialenvelope header, the first envelope header, and the modified secondEthernet packet are part of transmitting an envelope.
 2. The method ofclaim 1, wherein the generating of the modified second Ethernet packetcomprises: setting, in the second envelope header, a flag that indicatesthat the modified second Ethernet packet is encrypted; and encryptingthe modified second Ethernet packet.
 3. The method of claim 2, wherein:the generating of the modified second Ethernet packet comprises setting,in the second envelope header, a flag that corresponds to an encryptionmethod; and the encrypting of the modified second Ethernet packetcomprises encrypting the modified second Ethernet packet using theencryption method.
 4. The method of claim 1, wherein: the transmittingof the envelope comprises transmitting an Ethernet fragment after themodified second Ethernet packet.
 5. The method of claim 1, wherein theinitial envelope header further comprises: a 1-bit encryption flag; a1-bit key flag; an 8-bit cyclic redundancy check (CRC) field; and a6-bit envelope position alignment marker (EPAM) field.
 6. The method ofclaim 5, wherein: the EPAM field of the initial envelope header has avalue; and further comprising: generating, by the one or moreprocessors, a second initial envelope header that indicates that thesecond initial envelope header is not a preamble replacement, whereinthe second initial envelope header comprises a 6-bit EPAM fieldcontaining a value that is the same as the value of the EPAM field ofthe initial envelope header; and transmitting, over the PON, by the oneor more processors, the second initial envelope header.
 7. The method ofclaim 6, wherein: the transmitting of the initial envelope header overthe PON uses a first wavelength; and the transmitting of the secondinitial envelope header over the PON uses a second wavelength.
 8. Themethod of claim 1, wherein: the transmitting of the envelope comprisestransmitting an Ethernet fragment.
 9. The method of claim 8, wherein:the Ethernet fragment is after the initial envelope header and beforethe first envelope header.
 10. A system for transmitting Ethernetpackets over a passive optical network (PON) comprising: a memorystorage comprising instructions; and one or more processors incommunication with the memory storage, wherein the one or moreprocessors execute the instructions to perform: generating an initialenvelope header that indicates that the initial envelope header is not apreamble replacement; transmitting, over the PON, the initial envelopeheader; accessing an eight-byte block from a first Ethernet packet of aplurality of Ethernet packets; in response to the eight-byte block beingan Ethernet preamble, generating a first envelope header that indicatesthat the first envelope header is a preamble replacement; transmitting,over the PON, the first envelope header; generating a modified secondEthernet packet from a second Ethernet packet of the plurality ofEthernet packets by replacing a preamble of the second Ethernet packetwith a second envelope header that includes an indication that thesecond envelope header is a preamble replacement; and transmitting, overthe PON, the modified second Ethernet packet; wherein the transmittingof the initial envelope header, the first envelope header, and themodified second Ethernet packet are part of transmitting an envelope.11. The system of claim 10, wherein the generating of the modifiedsecond Ethernet packet comprises: setting, in the second envelopeheader, a flag that indicates that the modified second Ethernet packetis encrypted; and encrypting the modified second Ethernet packet. 12.The system of claim 11, wherein the generating of the modified secondEthernet packet comprises setting, in the second envelope header, a flagthat corresponds to an encryption method; and the encrypting of themodified second Ethernet packet comprises encrypting the modified secondEthernet packet using the encryption method.
 13. The system of claim 10,wherein: the transmitting of the envelope comprises transmitting anEthernet fragment after the modified second Ethernet packet.
 14. Thesystem of claim 10, wherein the initial envelope header furthercomprises: a 1-bit encryption flag; a 1-bit key flag; an 8-bit cyclicredundancy check (CRC) field; and a 6-bit envelope position alignmentmarker (EPAM) field.
 15. The system of claim 14, wherein: the EPAM fieldof the initial envelope header has a value; and the one or moreprocessors further perform: generating a second initial envelope headerthat indicates that the second initial envelope header is not a preamblereplacement, wherein the second initial envelope header comprises a6-bit EPAM field containing a value that is the same as the value of theEPAM field of the initial envelope header; and transmitting, over thePON, the second initial envelope header.
 16. The system of claim 15,wherein: the transmitting of the initial envelope header over the PONuses a first wavelength; and the transmitting of the second initialenvelope header over the PON uses a second wavelength.
 17. The system ofclaim 10, wherein: the envelope comprises an Ethernet fragment.
 18. Anon-transitory computer-readable medium storing computer instructions,wherein the instructions, when executed by one or more processors, causethe one or more processors to perform steps of: generating an initialenvelope header that indicates that the initial envelope header is not apreamble replacement; transmitting, over a passive optical network(PON), the initial envelope header; accessing an eight-byte block from afirst Ethernet packet of a plurality of Ethernet packets; in response tothe eight-byte block being an Ethernet preamble, generating a firstenvelope header that indicates that the first envelope header is apreamble replacement; transmitting, over the PON, the first envelopeheader; generating a modified second Ethernet packet from a secondEthernet packet of the plurality of Ethernet packets by replacing apreamble of the second Ethernet packet with a second envelope headerthat includes an indication that the second envelope header is apreamble replacement; and transmitting, over the PON, the modifiedsecond Ethernet packet; wherein the transmitting of the initial envelopeheader, the first envelope header, and the modified second Ethernetpacket are part of transmitting an envelope.
 19. The computer-readablemedium of claim 18, wherein the generating of the modified secondEthernet packet comprises: setting, in the second envelope header, aflag that indicates that the modified second Ethernet packet isencrypted; and encrypting the modified second Ethernet packet.
 20. Thecomputer-readable medium of claim 19, wherein: the generating of themodified second Ethernet packet comprises setting, in the secondenvelope header, a flag that corresponds to an encryption method; andthe encrypting of the modified second Ethernet packet comprisesencrypting the modified second Ethernet packet using the encryptionmethod.